Grade and payload estimate-based transmission gear selection

ABSTRACT

A vehicle includes an automatic transmission and a set of sensor inputs providing values indicating a current operational status of the vehicle pertinent to controlling the automatic transmission. The set of sensor inputs include: engine speed, engine torque, current transmission gear; and vehicle speed. The vehicle includes a programmed processor configured to iteratively and co-dependently generate a vehicle mass parameter value and a grade of incline parameter value. The programmed processor, when generating the vehicle mass parameter value and the grade of incline parameter value, uses a set of parameters including: a propulsive force driving the vehicle; a set of forces acting on the vehicle resisting forward movement, and an observed rate of change of a speed of the vehicle.

TECHNICAL FIELD

This disclosure relates generally to controlling transmission gearselection in heavy machinery, such as articulated trucks, havingautomatic transmissions. More particularly, the present disclosurerelates to heavy machines including automatic transmissions that arecontrolled according a selected one of multiple pre-defined transmissiongear selection schedules. The gear selection schedule is selected basedupon observed conditions indicative of power demand. Such conditionsinclude both operator demand (e.g., throttle position) and machine load(e.g., machine weight, grade of traveled surface, etc.).

BACKGROUND

Wheel-driven heavy machinery, such as articulated trucks andgraders/scrapers, operate under a wide variety of conditions thatrequire different amounts of driving force (i.e., torque) to be producedby an output of a drive train to propel the machinery. Such conditionsinclude surface types, grades, and cargo payload conditions. Moreover, avehicle drive train control takes into consideration the expectations ofa human operator, as indicated for example by a current throttleposition. Thus, at least one important aspect of the vehicle drive traincontrol is to take into consideration current operating conditions anddriver demand and render responsive vehicle drive train control commands(e.g., increase fuel/air flow, reduce/increase transmission gear ratio,etc.).

A transmission gear/shift selection control method is described inKresse U.S. Pat. No. 7,499,784. A shift schedule is selected for atransmission on an open-road (e.g., semi-trailer) truck based uponsensed conditions. In particular, the shift schedule is selected basedupon a vehicle mass and an estimated road grade. In the example, a roadgrade estimate is calculated based upon a current vehicle mass(including payload) and tractive effort by the drive train. The netforce causing acceleration of a truck is determined by subtracting avariety of forces (braking, drag, and grade) from the torque generatedby the drive train upon the wheels. A recursive least squares estimatorwith forgetting facilitates generating a first estimate of road gradefrom the aforementioned parameter values. A second grade estimateprovides an alternative grade value when poor signal-to-noise ratioconditions are detected. The vehicle mass estimate and a grade estimate,provided by one of the two alternative grade estimate sources, provideinputs to a transmission control that switches between performance (highpower) and economy (high mileage) modes.

Nitz EP App. Pub. No. 0 512 596 A1 describes a shift pattern control inwhich upshifting/downshifting is modified in response to changes in roadload. Above normal road load conditions can occur when a vehicle istowing a trailer, traveling a steep grade, and/or when unusualaerodynamic loading is encountered. When excessive road load is detecteda shift pattern is adopted characterized by earlier downshifting duringdeceleration and later upshifting during acceleration of a vehicletraveling under above normal road load conditions.

Shortcomings in the state of the art are addressed by aspects of anexemplary method and transmission assembly (including a controllerthereof) described herein.

SUMMARY OF THE INVENTION

A vehicle and method carried out by such vehicle are described herein.The vehicle includes an automatic transmission and a set of sensorinputs providing values indicating a current operational status of thevehicle and pertinent to controlling the automatic transmission. The setof sensor inputs include: engine speed, engine torque, currenttransmission gear; and vehicle speed. The vehicle furthermore includes aprogrammed processor configured by computer-executable instructions toiteratively and co-dependently generate a vehicle mass parameter valueand a grade of incline parameter value. The programmed processor, whengenerating the vehicle mass parameter value and the grade of inclineparameter value, uses a set of parameters including: a propulsive forcedriving the vehicle; a set of forces acting on the vehicle resistingforward movement, and an observed rate of change of a speed of thevehicle. The invention is furthermore embodied in a method carried outby a vehicle embodying the above functionality and a non-transitorycomputer readable medium including computer-executable instructions forexecution by a processor/controller to carry out the above-describedfunctionality.

BRIEF DESCRIPTION OF THE DRAWINGS

While the appended claims set forth the features of the presentinvention with particularity, the invention and its advantages are bestunderstood from the following detailed description taken in conjunctionwith the accompanying drawings, of which:

FIG. 1 is an outline view of a motor grader machine/vehicle, which isillustrated as one example of a machine suitable for incorporating aload/grade estimator and gear selection strategy in accordance with thedisclosure;

FIG. 2 is a block diagram representation of a programmed controller,automatic transmission and related components for an exemplary machinein accordance with the disclosure;

FIG. 3 a graphically depicts a set of power curves and operation of amachine traversing a series of gears in a standard manner;

FIG. 3 b graphically depicts a set of power curves and operation of amachine traversing a series of gears in accordance with a performancebased downshifting scheme for an automatic transmission;

FIG. 4 is a flowchart summarizing operation of an exemplary processcarried out by a programmed controller to manage an automatictransmission in accordance with the disclosure; and

FIG. 5 is a schematic depiction of a set of functional blocksincorporated into a configuration of a programmed processor forperforming mass and grade calculations based upon observed forces actingon a vehicle during operation.

DETAILED DESCRIPTION OF THE DRAWINGS

Before turning to the drawings, it is generally noted that thisdisclosure relates to vehicles including automatic transmissionsgoverned by a programmed controller to facilitate managing a gearselection (shift point) strategy based in part upon a power trainperformance parameter (e.g., power curve, torque curve, etc.), a payloadestimate, and a grade estimate. The payload and grade estimates aregenerated from a determination of the forces potentially acting upon avehicle in motion. Based upon the calculated payload and gradeestimates, the controller selectively triggers a shift control schedulefrom a set of pre-configured shift control schedules for the vehicle.For example, where a total resistive force exceeding the currentpropulsive force of the vehicle (at a currently selected gear) isencountered, a high output gear shift control schedule is triggered. Thehigh output gear shift control schedule, characterized by an earlydownshift during vehicle linear deceleration, maintains the drive trainat a high (power and/or torque) output while downshifting duringdeceleration of the machine due to encountering high resistance tomovement in the current direction of travel of the vehicle. In theillustrative example, the downshift control schedule is implemented tomaintain high power delivery as measured at a drive wheel/traveledsurface interface—referred to herein as “rim power” (power exerted bythe wheel outer edge/rim to propel a vehicle along a surface).

Encountering high resistance to vehicle movement along a traveledsurface can be attributed to a variety of sources including: carrying aheavy load, travelling a steep incline, implement/tool (e.g., graderblade) resistance, etc. The system and method described herein take intoconsideration multiple, potentially varying, sources of resistance tovehicle movement to determine, for example, an appropriate gear shiftschedule such as determining whether to trigger an early downshiftschedule for the automatic transmission, thus maintaining the output ofthe drive train at or near a maximum during a series of gear changes.

The transmission control strategy, implemented by the programmedcontroller, described herein includes two generalized functions. A firstfunction determines a final gear based upon a current determination ofpower train output torque, measured at the wheel/ground interface,needed to counter a current resistance to forward movement. By way ofexample, such resistance is a function of a measured grade that thevehicle is currently attempting to climb and a current vehicle mass. Themeasured grade is provided, for example, by an inertial measurementunit. The vehicle mass is determined by any of a variety of methods,including determinations based upon machine characteristics andphysics-based calculations (e.g. force=(mass)*(acceleration)).

A second function, of the two generalized functions, selects anappropriate downshift schedule based upon the final gear provided by thefirst function and a combination of factors including: a throttleposition, a load status, a machine acceleration, and a current gear. Thecombination of the first and second module functionalities facilitatesconsistent gear shift behavior while traversing a series of downshiftsnecessitated by encountering a high resistance to the propulsive forceprovided by a machine transmission.

Having briefly summarized the general functionality of an illustrativepayload and grade estimator used to trigger a performance gear shiftstrategy to facilitate operating at maximum rim power during a period ofdeceleration while climbing a steep grade, attention is directed to FIG.1 that provides an outline perspective view of one example of a machine100 incorporating such control scheme. In the illustration of FIG. 1,the machine 100 is a motor grader, which is one example for a machine toillustrate the concepts of the described payload and grade estimator,the output of which is used by a programmed controller for an automatictransmission to trigger a performance based gear selection strategy.While the arrangement is illustrated in connection with the motorgrader, the arrangement described herein has potential applicability invarious other types of machines, such as wheel loaders, articulatedtrucks, etc. The term “machine” refers to any machine that performs sometype of operation associated with an industry such as mining,construction, farming, transportation, or any other industry known inthe art. For example, the machine may be a dump truck, backhoe, grader,material handler or the like.

A motor grader is used in the description that follows as an example forillustration. A side view of a machine 100, in this example a motorgrader 101, is shown in FIG. 1. The motor grader 101, a machine having ahydrostatically operated propel circuit for moving the machine acrossthe terrain and a hydraulically operated implement circuit operating animplement for performing various machine tasks, is described herein forthe sake of illustration. However, any other mode of powering themachine is contemplated, for example, by use of electrically operatedmotors and/or actuators. For instance, an alternative embodiment for themachine 100 may include a generator or another device capable ofproducing an alternative form of energy, such as electrical power.

The motor grader 101 shown in FIG. 1 generally includes a two-pieceframe made up of an engine frame 102 and an implement portion 104.Alternatively, the motor grader 101 may include a single frame piece.The engine frame 102 in the embodiment shown is connected to theimplement portion 104 by a pivot (not shown). The implement portion 104includes an operator cab 106 and two idle wheels 108 (only one visible)that contact the ground. In the illustrative example the implement, ablade 110, is suspended along a mid-portion of the implement portion104. The blade 110 can be selectively adjusted to engage the ground atvarious heights and angles to achieve a desired grade or contour whilethe motor grader 101 operates. Adjustment of the position of the blade110 is accomplished by a system of actuators, generally denoted in FIG.1 as 112, while support for the loading experienced by the blade 110during operation is accomplished by a bar 114, which pivotally connectsthe implement portion 104 to the blade 110.

The engine frame 102 supports an engine (not visible), which isprotected from the elements by an engine cover 116. The engine providesthe power necessary to propel the motor grader 101 as well as to operatethe various actuators and systems of the motor grader 101. As can beappreciated, other machines may have different configurations and/orvarious other implements associated therewith.

In a hydrostatically operated machine, the engine in the engine frame102 may be associated with a hydrostatic pump (not shown), which may bepart of a hydraulic system operating a propel system of the motor grader101. In the embodiment shown, the motor grader 101 is driven by two setsof drive wheels 118 (only one set visible), with each set including twodrive wheels 118 that are arranged in a tandem configuration along abeam 120. Two beams, one being the beam 120, are pivotally connected onthe ends of a shaft or axle at a respective pivot joint or bearing 123,with the beam 120, of the two beams, disposed on one side of the motorgrader 101.

At least one or both of the two drive wheels 118 on the beam 120 may beactively rotated or driven by a corresponding motor. When only one wheelof the two drive wheels 118 is powered, the other wheel may be idle or,stated differently, may be free to rotate relative to the beam 120.

A simplified block diagram of a power delivery system 200 for a machineincluding an automatic transmission, for example, the machine 100 (FIG.1), is shown in FIG. 2. The power delivery system 200 includes atransmission 202. The transmission 202 is arranged to transmit powerfrom an engine (not shown) to systems that propel or otherwise move themachine. In the illustrative example, the transmission 202 providespower, via a propel power 204 output to one or more systems that operateto move the machine, which is/are shown collectively as a machine propelsystem 206.

The machine propel system 206 provides a motive force for the machine100. The propel power 204 output is provided in any suitable formincluding, for example, mechanical power from a rotating transmissionoutput shaft. The machine propel system 206 includes one or moremechanical drives that are arranged to rotate or otherwise actuatecomponents providing force for driving, for example, one or more wheelsof the machine 100.

In the illustrative embodiment, the power delivery system 200 includes aprogrammed controller 214. The programmed controller 214 is, forexample, a single controller or alternatively includes more than onecontroller disposed to control various functions and/or features of themachine 100. The programmed controller 214, by way of example, includesa gear selection logic module 216 comprising computer-executableinstructions that facilitate performing a transmission control strategydescribed herein. In particular, the gear selection logic module 216includes a first function that determines a final gear based upon acurrent determination of power train output torque needed to counter acurrent resistance to movement of the machine 100 on a traveled surface.By way of example, such resistance is a function of a measured and/orcalculated grade that the vehicle is currently attempting to climb and acurrent vehicle mass. The grade is provided, for example, by an inertialmeasurement unit. Alternatively, the grade is calculated indirectly fromoperational parameters indicative of a currently traveled grade. Thevehicle mass is determined by any of a variety of methods, includingdeterminations based upon machine characteristics and physics-basedcalculations (e.g. force=(mass)*(acceleration)).

The gear selection logic module 216 includes a second function forselecting an appropriate downshift control schedule (a series ofdownshift points) based upon the final gear provided by the firstfunction and a combination of factors including: a throttle position, aload status, a machine acceleration, and a current gear. A throttleposition signal is provided, for example, from an operator controldevice 224 via an operator control signal line 226. Other potentialinput signals from the operator control device 224 via control signalline 226 include a cruise control signal.

In the illustrated embodiment, the power delivery system 200 includesvarious links disposed to exchange information and command signalsbetween the programmed controller 214 and the various systems of themachine 100. Such links are of any appropriate type, and may be capableof two-way exchange of multiple signals. In one embodiment, such linksare channels of communication between various devices that are connectedto one another via a controller area network (CAN). More specifically, aspeed sensor link 218 interconnects the programmed controller 214 with atransmission output speed sensor 219. The speed sensor link 218 providesa signal indicative of the output speed of the transmission 202 which,in turn facilitates calculating a variety of other parameter valuesincluding machine speed and rate of change of the machine speed forpurposes of determining current rate of deceleration of the machinewhile, for example, climbing a hill.

The set of signals received by the programmed controller 214 includesthe following parameters that may be used by the gear selection logic:acceleration (in direction of machine travel), machine incline/slope(estimated or measured), and motor speed (motor RPM).

During operation of the power delivery system 200, the programmedcontroller 214 may be configured to receive and process informationrelating to determining torque/force or power utilization by the varioussystems, for example the machine propel system 206. The programmedcontroller 214 determines drive force exerted, and power delivered, bythe propel power 204 output.

Alternatively, instead of using the transmission output speed, an actualcurrent velocity of the machine 100 may be derived, for example, from afiltered stream/series of instantaneous acceleration signals provided byan accelerometer 240. The filtered acceleration signal specified by theaccelerometer 240 may be normalized, when calculating velocity formachine travel on a non-level travel surface, using a signal provided bya slope sensor 242. The slope sensor 242 specifies the grade upon whichthe machine is traveling (in a forward direction).

The programmed controller 214 is, by way of example, connected to thetransmission 202 by two communication links, a transmission output link228 and a transmission input link 230. The transmission output link 228represents the ability of the programmed controller 214 to providecommand signals to various transmission actuators and systems thatcontrol the operation of the transmission 202. Information signals thatare indicative of one or more transmission operating parameters areprovided to the programmed controller 214 via the transmission inputlink 230. As discussed above, the transmission input link 230 and thetransmission output link 228 are embodied in any appropriatearrangement, for example, by use of CAN links that are capable oftransferring more than one signal at the same time, but otherarrangements may be used.

It will be appreciated that the programmed controller 214 discussedherein is a computing device, e.g., a programmed processor, which readscomputer-executable instructions from a computer-readable medium andexecutes those instructions. Media that are readable by a computerinclude both non-transitory and transitory media. Examples of the formerinclude magnetic discs, optical discs, flash memory, RAM, ROM, tapes,cards, etc. Examples of the latter include acoustic signals, electricalsignals, AM and FM waves, etc. As used in the appended claims, the term“non-transitory computer-readable medium” denotes tangible media thatare readable by a computer unless otherwise specifically noted in theclaim.

Having described an exemplary machine and power control arrangement(FIG. 2), attention is now directed to FIGS. 3 a and 3 b that, together,illustratively depict an exemplary transmission gear selection strategy(FIG. 3 b). The illustrative strategy maintains engine power at aconstantly highest output during deceleration of the machine 100 that,in turn, necessitates performing a series of downshifts to stop theunintended deceleration. Such deceleration is caused, for example, byencountering a high resistance to forward movement due to a combinationof factors including the machine attempting to climb a large uphillgrade while carrying a large payload or machine tool load (e.g., anengaged grader blade).

In the illustrative example, FIG. 3 a graphically depicts a typicaltransmission downshift scheme. In the example, line 300 depicts a rimpower path where downshifting is performed as a vehicle decelerates suchthat a substantial power jump occurs in response to each downshift geartransition.

In contrast to the rim power path of FIG. 3 a, a rim power path 310 ofthe machine 100 operating in accordance with a high performancedownshift series is depicted in FIG. 3 b wherein downshifting occurs atcrossover points of the power curves for adjacent gears. In theillustrative example of FIG. 3 b, downshifting occurs relatively earlierfor each downshift between adjacent gears for a series of downshiftsfrom fifth gear down to first gear, in comparison to the downshiftschedule depicted in FIG. 3 a. For example, in FIG. 3 a, downshiftingfrom third to second gear occurs at approximately 17 miles per hour(vehicle speed). At this point, the engine speed (rpm) is sufficientlyslowed such that a significant power drop off has occurred while themachine continues to operate in the higher gear. However, in accordancewith an early downshift arrangement depicted in FIG. 3 b, downshiftingfrom third to second gear occurs at a power curve crossover point atapproximately 20 miles per hour. Initiating downshifts before poweroutput of the engine has substantially fallen off (e.g., at power curvecrossover points between adjacent gears) enables greater total poweroutput by the engine during the series of downshifts from fifth to firstgears according to the downshift schedule depicted in FIG. 3 b—incomparison to the series of downshifts occurring during the exampleprovided in FIG. 3 a. A method, carried out by the gear selection logicmodule 216, is described herein below with reference to FIG. 4. Themethod includes identifying circumstances necessitating a series ofdownshifts from a current gear to a destination gear enabling thetransmission 202 to supply sufficient torque to the machine propelsystem 206, via the propel power 204 output, to counter/overcome acurrent total resistance force encountered by the transmission 202 ofthe machine 100.

FIG. 4 summarizes a set of steps for a process 400, repeatedly (e.g.,periodically or in response to a triggering event) carried out by themachine 100 under the direction of the programmed controller 214. Thesummarized steps relate to detecting a triggering event and thereafterimplementing a gear shift control strategy in accordance with thedownshift arrangement depicted in FIG. 3 b to maximize performance(power output) while performing a series of sequentially executeddownshifts to a destination gear. The destination gear is determinedbased upon a current resistance to forward movement encountered by themachine 100. Such resistance is at least based upon a current inclinegrade and a mass of the machine 100 (including payload). However, suchcalculation may also incorporate a variety of other contributors toforward movement resistance (described herein below with reference toFIG. 5). The process 400 is exemplary. Thus, variations are contemplatedfor controlling, based on various observed machine parameters, thetriggering of the downshift schedule illustratively depicted in FIG. 3b. The method summarized in FIG. 4 is aided by a payload and gradeestimator described herein below with reference to FIG. 5.

During step 405 the programmed controller 214 calculates a currentresistance to forward movement of the machine 100. Such calculation isbased at least upon a current grade of an incline as well as a currentmass of the machine 100 as calculated by the programmed controller 214.A particular example of a configuration of the programmed controller 214to provide the current mass and grade calculations is provided in FIG. 5described herein below. In the illustrative example, the forwardmovement resistance calculation also takes into consideration aresistive force attributed to a machine implement/tool, such as adeployed scraper blade on a grader machine.

During step 410, the programmed controller 214 applies the resistance toforward movement calculated during step 405 to a set of torquecharacteristics for each of the forward operating gears of the machine100 to determine a destination gear for the machine 100. By way ofexample, the destination gear is a highest gear at which sufficienttorque is generated, by the transmission 202 and propel power 204output, to exceed the current forward movement resistance calculatedduring step 405. Control then passes to step 415.

If, during step 415, the programmed controller 214 detects a triggercondition for activating the early downshift schedule for the machine100 such as the downshift schedule illustratively depicted in FIG. 3 b,then control passes to step 420. By way of example, the triggercondition may comprise any one or more of a set of individual/combinedconditions based upon a set of inputs including, for example: throttleposition, current gear, rolling resistance, grade, current total vehiclemass, calculated destination gear. For example, in an exemplaryembodiment, the early shift schedule unless the calculated destinationgear is at least two less than the current gear. Thus, the early shiftstrategy is intended to be entered when a prolonged substantial torquedeficit is likely to be encountered by the machine that requiresdownshifting to a destination gear in order produce an output torquethat exceeds the current resistance force calculated during step 405. Ifno trigger condition is detected, then control passes from step 415 tothe End.

The illustrative control process described herein above with referenceto FIG. 4 can be modified and/or enhanced through use of additionaland/or alternative sensors.

Having described an exemplary operation of the programmed controller 214gear selection logic module 216 to detect and execute an early geardownshift schedule based upon a current forward movement resistance,attention is directed to FIG. 5 summarizing a configuration of theprogrammed controller 214 that facilitates generating a machine mass andgrade (incline) that is used to calculate such force of resistance toforward movement for the machine 100 during step 405 of FIG. 4.

An inputs block 500 represents a set of input parameters used by theprogrammed controller 214 to perform grade and mass calculations. Theinput parameters provided by inputs block 500 include, by way ofexample: a speed ratio, engine speed, engine torque, currenttransmission gear, and vehicle speed. The input parameters are providedto a set of intermediate calculation blocks (described below) that, inturn, provide their output to a mass calculator 502 and a gradecalculator 504. Estimated mass and grade values, generated by the masscalculator 502 and a grade calculator 504, are advantageously providedto the gear selection logic module 216 to control gear selection. Whilethe mass and grade estimates are used in the early downshift strategydiscussed herein above (see FIG. 4), the gear selection logic module 216uses the calculated mass and grade estimates—even in cases where theearly gear downshift mode is not activated—to control transmission gearselections to enhance performance and/or fuel economy of the machine100.

The operation of the mass calculator 502 and the grade calculator 504 isperformed iteratively and in parallel. The mass calculator 502 generatesa mass estimate M according to the equation:M=(Fprop−Frolling−Fair−Finertia)/((veh acceleration)+((accel ofgravity)(sin(grade))))

The grade calculator 504 generates a grade estimate G according to theequation:G=a sin((Fprop−Frolling−Fair−Finertia−(veh accel)(mass))/((mass)(accelof gravity)))

Moreover, the mass and grade calculations are co-dependent. Thus, theoutput values of the mass calculator 502 are passed to the gradecalculator 504 to facilitate grade calculations, and the output valuesof the grade calculator 504 are passed to the mass calculator 502 tofacilitate mass calculations. The iterative sharing of mass and gradeestimate calculations by the mass calculator 502 and grade calculator504 creates a self-correcting co-dependent relationship between the masscalculator 502 and the grade calculator 504 that avoids the necessity toimplement error correction algorithms such as the recursive leastsquares algorithm described, for example, by Kresse U.S. Pat. No.7,499,784.

As explicitly depicted in FIG. 5, a mass calculation filter/averager 503and a grade calculation filter/averager 505 may be implemented on inputand/or output values for the mass calculator 502 and grade calculator504 to provide a degree of temporal stability to mass and gradecalculations in the short term. As will be appreciated in view of theillustrative embodiments, the filter/averager functionality can beimplemented in a variety of ways using any of a variety offiltering/averaging schemes. By way of example, a weighted movingaverage window, specifying a sequence of x coefficients (weights)totaling a value of 1, is applied to a sequence of previously calculatedvalues including: (1) a current value rendered by the mass calculator502 or grade calculator 504, as well as (2) x−1 previously calculatedvalues rendered by the mass calculation filter/average 503 or gradecalculation average 505.

Moreover, multiple filter/averager definitions can be provided. First,distinct filter/averager definitions are provided for processing theoutput of the mass calculation filter/average 503 and the gradecalculation filter/averager 505. Second, multiple distinctfilter/averager definitions are provided, and dynamically specified,based upon an current general operation state of the machine. Suchstates include, for example, a starting/accelerating from a stoppedstate, a gear shift, a steady rolling state. In such distinctoperational states, different sets of coefficients are used to resist oraccept current changes to calculated mass and grade values rendered bythe mass calculator 503 and grade calculator 505. Other tunable aspectsof the filter/averager definitions include the time delay betweencalculations of new mass and grade values and the number of total values(x) falling within the averaging window (in the illustrative example).

The description below is directed to the sources of parameter values(see FIG. 5) for the above identified parameters used by the masscalculator 502 and the grade calculator 504. A propulsive forcecalculator 510 provides the Fprop parameter value, the force generatedat the output of the transmission, based upon the following equation:Fprop=((Eng trq)(Cnvrtr Trq Ratio)−(Xmsn Losses))/(Overall Radius)

The Engine Torque (Eng trq) parameter value is based upon a reportedengine torque value provided to a converter absorption block 514 fromthe inputs block 500. The actual torque delivered at the transmissionoutput is provided by the converter absorption block 514 based upon aset of provided parameters that impact the operation of the torqueconverter. In particular, the converter absorption block 514 determineswhether the converter is in lock-up or converter mode. When the torqueconverter is operation in lock-up mode, converter absorption block 514passes the reported engine torque (from the inputs block 500) to thepropulsive force calculator 510 in its unmodified form (i.e., the enginetorque value provided by the inputs block 500). However, if the torqueconverter is operating in the “converter” mode, the converter absorptionblock 514 adjusts (reduces) the reported engine torque value receivedfrom the inputs block 500 according to a conversion table/equation basedupon current machine operating parameter values including: reportedengine torque (from inputs block 500), speed ratio (ratio of torqueconverter input to converter output), and engine speed (from inputsblock 500).

The Converter Torque Ratio (Cnvrtr Trq Ratio) is provided by a convertertorque ratio block 512 based upon a speed ratio parameter value providedby the inputs block 500 based upon the converter input speed andconverter output speed. The Transmission Losses (Xmsn Losses) parametervalue accounts for force losses attributable to rotation/movement of thetransmission components. The transmission losses force value isdynamically generated by the propulsive force calculator 510 based uponspeed ratio, engine speed and transmission gear parameter valuesprovided by the inputs block 500.

The Overall Radius parameter value corresponds to the rolling radius ofa driven wheel on a driven surface (e.g., the distance from the centerof the driven wheel to the ground)

Having described the functionality of the propulsive force calculator510, attention is directed to a set of additional functional blocks thatprovide input parameter values to the mass calculator 502 and the gradecalculator 504. A Rolling Force calculator 520 provides the Roll Forceparameter value, the rolling resistance caused by a surface upon whichthe vehicle's wheels are travelling, based upon the following equation:Roll Force(Frolling)=0.0041+(vehiclespeed)(0.000041)(mass)cos(grade)+(implement/tool force)

The Rolling Force calculator 520 receives input mass and grade valuesfrom the mass calculator 502 and the grade calculator 504, and receivesthe vehicle speed from the inputs block 500. The Rolling Forcecalculator 520 is intended to be a customizable block wherein a constantand/or coefficient (e.g., 0.0041 and 0.000041) can be modified in eitherthe short term (e.g., when an implement such as a grader blade isdeployed) or long term (working on soft soil, travelling on a road,etc.).

Moreover, the Rolling Force calculator 520 is configured to account forforces attributable to a tool/implement that is deployed in a mannerthat either aids/resists movement of the machine to which it is attached(e.g., the tool is engaged with the ground). In the case of the motorgrader 101, a sensor (e.g., pressure transducer) provides a signalrepresentative of an implement (e.g., blade 110) resistance force. Theimplement resistance force is represented by the “implement/tool force”term in the above provided Roll Force equation. The signalrepresentative of the implement resistance force may be filtered tosmooth the signal over the short term and reject/minimize transientsensor spikes that should not substantially affect long-term rollingresistance calculations performed by the Rolling Force calculator 520.

A Force of Air calculator 530 provides the Air Force parameter value,the resistance created by drag as a vehicle moves through air, basedupon the following equation:Air Force=(drag coefficient)(frontal area)(vehicle speed^2)/2

The Force of Air calculator 530 receives an input vehicle speed valuefrom the inputs block 500. The frontal area is provided based uponprevious measurements, and the drag coefficient is provided fromprevious measurements for the type of the machine 100 under variousconditions.

A Force of Inertia calculator 540 provides the Inertia Force parametervalue, the force needed to accelerate the transmission and other drivetrain components of the machine 100, based upon a current vehicleacceleration (i.e., change in linear speed per time unit) and a currenttransmission gear. The current transmission gear is provided by theinputs block 500. The vehicle acceleration is provided by anacceleration calculator 550 based upon a series of input vehicle speedsover specified time periods. It is particularly noted that thetransmission gear input parameter value (indicating the current gear ofthe machine) may be very important to accurate calculations by both themass calculator 502 and the grade calculator 504 in machines where theinertial forces vary widely according to selected gear due to theirsubstantial mass.

Having described the input values and calculations performed by anexemplary configuration of the programmed controller 214, it is furthernoted that in some instances it is beneficial to freeze or even resetcalculations by the mass calculator 502 and the grade calculator 504. Inthe illustrative example provided in FIG. 5, a reset/hold logic block506 guards against potentially unusual input parameter values that maylead to undesirable erratic behavior by the gear selection logic module216. In particular, the reset/hold logic block 506 receives input valuesfrom the inputs block 500 indicative of current operating conditions forthe machine 100 that call for either resetting or holding valuespreviously calculated by the mass calculator 502 and/or the gradecalculator 504. Based upon the received input values from inputs block500 the reset/hold logic block 506 conditionally issues freeze or resetsignals to one or both of the mass calculator 502 and the gradecalculator 504. For example, the mass value generated by the masscalculator 502 is reset to the empty load value, when the machine 100 isan articulated truck, when a load ejector button is activated. Also, thereset/hold logic block 506 issues a signal freezing operation of boththe mass calculator 502 and the grade calculator 504 any time themachine 100 is turning due to the complex forces acting upon the machine100 such operation.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to driven machines having anautomatic transmission controlled and configured to deliver a variablepropulsive force to drive wheels of a machine. In particular, thedisclosed principles provide a mechanism for maintaining engine poweroutput at a higher level during a series of downshifts necessitated bythe machine encountering an increased resistance to forward movement ofthe machine as a result of, for example, encountering a hill having arelatively steep grade. This system may be implemented in a variety ofmachines that operate under a variety of propulsive load conditions andare likely to experience substantially increased forward movementresistance during normal operation. Although many machines that maybenefit from the disclosed principles will be machines used in off-roadmachines such as graders and off-road articulated dump trucks/haulers,it will be appreciated that the disclosed machines and programmedcontroller process for such machines are used in other contexts as well,and the teachings are likewise broadly applicable.

Using the disclosed principles, the programmed controller 214 controls atransmission to ensure that the propulsion system operates at a highpower output wherein gear downshifts occur, during deceleration of themachine, at the power curve cross-over points for adjacent gears. Itwill be appreciated that this description provides examples of thedisclosed system and technique. However, it is contemplated that otherimplementations of the disclosure may differ in detail from theforegoing examples. Moreover, the references to examples herein areintended to reference the particular example being discussed at thatpoint and are not intended to imply any limitation as to the scope ofthe disclosure more generally. All language of distinction anddisparagement with respect to various features is intended to indicate alack of preference for those features, but not to exclude such from thescope of the disclosure entirely unless otherwise indicated.

Recitation of ranges of values herein are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein, and eachseparate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order and from any suitable step unlessotherwise indicated herein or otherwise clearly contradicted by context.

What is claimed is:
 1. A vehicle including: an automatic transmission; aset of sensor inputs providing values indicating a current operationalstatus of the vehicle and pertinent to controlling the automatictransmission, the set of sensor inputs including: engine speed; enginetorque; current transmission gear; and vehicle speed; and a programmedcontroller configured by computer-executable instructions to iterativelyand co-dependently generate both a vehicle mass parameter value and agrade of incline parameter value, the programmed controller using a setof parameters including: a propulsive force driving the vehicle; a setof forces acting on the vehicle resisting forward movement, and anobserved rate of change of a speed of the vehicle, whereinco-dependently generating both the vehicle mass parameter value and thegrade of incline parameter value comprises using a previously generatedvehicle mass parameter value to generate a current incline parametervalue, and using a previously generated incline parameter value togenerate a current vehicle mass parameter.
 2. The vehicle of claim 1wherein a mass calculator of the programmed controller carries outgenerating the vehicle mass parameter value, and wherein the programmedcontroller is further configured to include a reset/hold logicfunctionality that selectively issues a command to the mass calculatorto reset a current value for the vehicle mass parameter value during aperiod of mechanical instability.
 3. The vehicle of claim 2 wherein theperiod of mechanical instability arises from a turning operation of thevehicle.
 4. The vehicle of claim 2 wherein the period of mechanicalinstability arises from a dumping operation by the vehicle.
 5. Thevehicle of claim 1 wherein the set of forces acting on the vehicleresisting forward movement include an actuable implement/tool force. 6.The vehicle of claim 1 wherein the set of forces acting on the vehicleresisting forward movement include a force of inertia arising from atransmission, and wherein a value for the force of inertia is determinedat least in part by a currently selected operating gear of the vehicle.7. The vehicle of claim 1 wherein the set of forces acting on thevehicle resisting forward movement include a traveled surface-dependentforce.
 8. The vehicle of claim 1 wherein the set of forces acting on thevehicle resisting forward movement include a speed-dependent airresistance force.
 9. The vehicle of claim 1 wherein the programmedcontroller is further configured to select a shift control schedulebased upon the generated vehicle mass parameter value and the grade ofincline parameter value.
 10. The vehicle of claim 1 wherein the grade ofincline is rendered by a grade calculator based upon a set of forcesoperating upon the vehicle, the mass resulting in linear acceleration ofthe vehicle.
 11. The vehicle of claim 1 wherein the grade of incline isrendered from a direct measure of current grade.
 12. The vehicle ofclaim 1 wherein the programmed controller includes a filter/average forrendering a filtered/averaged output value for at least one of the groupconsisting of: the vehicle mass parameter value and the grade of inclineparameter value.
 13. A method, performed by a programmed controllerconfigured by computer-executable instructions, for providing a vehicleparameter value pertinent to control of an automatic transmission withina vehicle including an automatic transmission, the vehicle generating aset of sensor inputs providing values indicating a current operationalstatus of the vehicle and pertinent to controlling the automatictransmission, and wherein the set of sensor inputs include: enginespeed, engine torque, current transmission gear; and vehicle speed, themethod comprising: iteratively and co-dependently performing, by theprogrammed controller, the steps of: generating a current vehicle massparameter value based upon a previously generated grade of inclineparameter value, and generating a current grade of incline parametervalue based upon a previously generated vehicle mass parameter value,wherein, in addition to the previously generated grade of inclineparameter value, the generating the vehicle mass parameter is based upona set of parameters including: a propulsive force driving the vehicle, aset of forces acting on the vehicle resisting forward movement, and anobserved rate of change of a speed of the vehicle; and issuing, by theprogrammed controller, an output signal to the automatic transmission,the output signal being based upon at least one of the current vehiclemass parameter value and the current grade of incline parameter value.14. The method of claim 13 further comprising: issuing a command toreset a current value for the vehicle mass parameter value during aperiod of mechanical instability.
 15. The method of claim 14 wherein theperiod of mechanical instability arises from a dumping operation by thevehicle.
 16. The method of claim 14 wherein the period of mechanicalinstability arises from a turning operation of the vehicle.